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Relativity of Simultaneity 
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#37
Feb1112, 07:35 AM

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#38
Feb1212, 04:23 PM

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A simple minded thought experiment: picture an x,y plot....as two particles move around there in different paths, they experience different rates of x and y distances covered,,,right? we don't normally think much about that......each would observe the other moving differenty through space [distance] than themselves.... now consider a plot of time versus,say, x distance: observe two particles moving differently.... say straight lines with different slopes as an example....one moves faster thru time and another faster thru distance [space]. We observe the particles and each observe's the other moving differently through time and the x direction than themselves....all the observations are 'correct' but they are also 'different'. 


#39
Feb1212, 07:30 PM

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Where I am not clear is why there is absolute simultaneity according to Lorentzian relativity but RoS according to Einsteinian. Do both not use the same transformations? 


#40
Feb1212, 10:02 PM

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http://www.physicsforums.com/showpos...22&postcount=2 And I stated it clearly here: http://www.physicsforums.com/showpos...5&postcount=57 http://www.physicsforums.com/showpos...9&postcount=59 http://www.physicsforums.com/showpos...7&postcount=11 


#41
Feb1212, 10:49 PM

P: 359

I do appreciate your taking the time to entertain my questions, and I'm sure you're probably addressing countless other [perhaps equally naiive] questions, so it will hopefully reduce any frustration you might be feeling by highlighting why I still haven't got my head around the issue, despite your generous attempts to clarify it. My trouble with "getting it" lies in the difference, or lack thereof, between Einsteinian relativity and Lorentzian relativity; do I understand correctly that there is essentially no difference between the mathematics of both interpretations? If so, the trouble I have is understanding how one interpretation includes RoS while the other includes absolute simultaneity. George suggested that it is down to the different assumptions about the propagation of light, but I don't see how that would lead to RoS without some intermediary step(s). If my understanding is correct, and the mathematics is the same for both theories, then I'm not sure a mathematical explanation will address the issue; I would imagine it has to be more of a theoretical consideration of what the maths represents. 


#42
Feb1312, 02:20 AM

P: 67

Hello Mangaroosh,
May I suggest yet another way of answering your two questions about Relativity of Simultaneity [RoS]? You might find it simpler to understand, and I am confident that DaleSpam, Ghwellsir, and other posters who have been answering your questions so tirelessly will vouch for its correctness: Your OP question is, Relativity of Simultaneity means simply that two events, separated by a distance from one another, and simultaneous according to one competent observer are not (generally) simultaneous according to another moving relative to the first at some constant speed. The simultaneity of two events can be established using a shuttered lamp on a track between two distant mirrors positioned on the track to reflect any light pulses from the lamp back to it and yourself, the observer. The mirrors need not be at rest and may move independently at arbitrary speeds along the track. Suppose that you are very quick with the shutter and send an extremely brief pulse of light towards both mirrors. If the reflected pulses from both mirrors happen to return simultaneously, what can you legitimately infer? Since by Einstein's postulate, light moves at one speed only, you know these two things: 1. the mirrors were equidistant from the lamp at the time of the reflection, and 2. the two reflections occurred simultaneously. Now suppose that a second observer happens to be moving along the track just as you send your light pulse from the lamp. Will he agree that the reflections were simultaneous? No. By the time the two reflected pulses meet at your lamp, observer #2 has moved some distance along the track, and correctly notes that the two pulses did not "return" simultaneously to his "here", and for that reason, by Einstein's postulate he must infer that the two reflections did not occur simultaneously. The LET interpretation predicts exactly the same phenomena, but differs from SR only in that it insists that light depends upon a hypothetical medium, or aether, Therefore the method of "simultaneous arrival" for determining simultaneity is valid only for an observer who is motionless in the aether, and there is only one "true" definition of simultaneity  that of the motionless observer. Einstein's great insight was that the aether hypothesis was completely superfluous.  Regards 


#43
Feb1312, 05:17 AM

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#44
Feb1312, 05:24 AM

P: 3,188

http://physicsforums.com/showpost.ph...3&postcount=54 Harald 


#45
Feb1312, 06:11 AM

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#46
Feb1312, 06:17 AM

P: 152

http://en.wikipedia.org/wiki/Relativity_of_simultaneity
From wikipedia: I think this type of thought experiments are always what is meant when someone talks about "relativity of simultaneity", but I might be wrong... 


#47
Feb1312, 06:27 AM

P: 359

I hope I'm using the right phraseology here when I say that, under Galilean transformations we would expect the moving observer to measure a different speed of light to the pulse operator, but under Lorentz transformations this isn't the case; is that accurate? Lorentzian relativity maintains absolute simultaneity, while Einsteinian relativity incorporates RoS. I don't think we're too concerned with Lorentzian relativity in this particular instance, what we're looking for, or rather, what I'm trying to understand, is what phenomena must occur in order for the speed of light to remain constant for all observers, regardless of their motion realtive to the source of the light; which appears to be the reason given, why RoS prevails. That was essentially the point made by George, so I presume he would agree with your statement to a similar effect. One thing he might disagree on is that Lorentzian relativity necessarily includes the superfluous concept of an aether. 


#48
Feb1312, 06:57 AM

P: 359

I had a quick glance at the reference in post #31, but statement immediately following the link was something you had mentioned before, with respect to detecting absolute simultaneity (or the time on a distant clock) and which I had addressed in #18; so that affected my judgement of the necessity to go through it in detail. Is there a specific part that I can jump to that would address the issue? Just reading back over the exchange I realise that I didn't address reply in #20 directly. I tried reformulating the question, which lead to your reply in #28, which appears to just be a reformulation of the same reply that was questioned previously. Post #20: This is #28, which, as mentioned, appears to just reformulate the issue of detecting absolute simultaneity. 


#49
Feb1312, 07:12 AM

P: 359

I'll PM you the reply, but I'd prefer to continue the discussion in an open thread. Perhaps if I PM you, you might be able to paraphrase the quote in your reply, for the posterity of the thread  that is if you deem it worthy of reply, of course. 


#50
Feb1312, 07:14 AM

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#51
Feb1312, 07:16 AM

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#52
Feb1312, 07:27 AM

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What phenomena occur that means the speed of light is c "in any inertial frame"? We would, ordinarily, expect the moving observer to measure a different speed of light  why is this not the case? 


#53
Feb1312, 07:53 AM

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#54
Feb1312, 08:24 AM

P: 152

However, in Special Relativity the Time Dilation formula kicks in and it so happens that if the guy on the platform would expect it to take a factor k longer for the light to reach the back and front wall and get back to the guy on the train again, then the time for the guy on the train slows down with the same factor k so he thinks the two way speed of light has the same value, c, no matter what the velocity of the train relative to the ground is... In this way the "twoway speed of light is the same in all inertial frames". I belive this is how it is always explained... 


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